3. Atoms are really, really small…… We can not work with individual atoms or AMU’s in the lab. Atomic Mass Unit WHY? Because we can’t see things that small!

4. We as scientists work with portions of matter large enough for us to SEE and MASS on a balance using units of……

5. This presents a problem….. A pile of atoms large enough for us to see contains billions of atoms. Copper (II) Sulfate So how would we keep track of that many atoms?

6. Chemists came up with a new unit.

7. Equivalents or Conversion Factors 1 dozen eggs = 12 eggs 1 rooster = two legs 1 ream of paper = 500 pieces of paper

8. Equivalents or Conversion Factors 1 mole = 6.02 x 10 23 There are EXACTLY 12 grams of Carbon-12 in 1 mole of Carbon-12.

9. Avogadro’s Number 6.02 x 10 23 He studied gases and discovered that no matter what the gas, there were the same number of molecules present. Named in honor of Amadeo Avogadro. 1776 - 1856 I did not discover the number. It was just named after me.

10. Units for Avogadro’s Number 1 mole = 6.02 x 10 23 (many different units) For instance: 1 mole of pennies = 6.02 x 10 23 pennies. This amount is equivalent to 7 stacks of pennies from the Earth to the moon.

11. Units for Avogadro’s Number 1 mole Mg= 6.02 x 10 23 atoms. 1 mole NaCl= 6.02 x 10 23 molecules. 1 mole Cl 2 = 6.02 x 10 23 molecules. 1 mole SO 4 -2 = 6.02 x 10 23 ions. Remember: HOFBrINCl

12. Calculating Formula Mass Calculate the formula mass of NaCl. 6 Na 22.9897 17 Cl 35.453 22.99 g + 35.45 g = 58.44 g Therefore, 1 mole of NaCl (6.02 x 10 23 molecules) has a mass of 58.44 g

13. Calculating Formula Mass Calculate the formula mass of K 2 O. 19 K 39.0983 6 O 15.9994 2(39.10) g + 16.00 g = 94.2 g Therefore, 1 mole of K 2 O (6.02 x 10 23 molecules) has a mass of 94.2 g

14. Calculating Formula Mass Calculate the formula mass of (NH 4 ) 2 SO 4. 7 N 14.0067 6 O 15.9994 2(14.01) g + 8(1.01) g + (32.01) + 4(16.00) g = 132.11 g Therefore, 1 mole of (NH 4 ) 2 SO 4 (6.02 x 10 23 molecules) has a mass of 132.11 g 1 H 1.00794 16 S 32.066

15. Calculating Formula Mass Calculate the formula mass of CuSO 4 5 H 2 O. 29 Cu 63.546 6 O 15.9994 63.55 g + 32.01g + 4(16.00) g + 5[2(1.01)+16.00] = 249.56 g 1 H 1.00794 16 S 32.066. Therefore, 1 mole of CuSO 4 5 H 2 O (6.02 x 10 23 molecules) has a mass of 249.56 g. This type of formula is called a hydrate. It is a salt with water physically attached to it. Example: A salt container with rice intermixed. Since the water is physically attached how could it be removed? By heating. When the water is removed the remaining salt is called anhydrous.